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Half the world’s population will have a mental health disorder by age 75

One in two people will develop a mental health disorder in their lifetime, with depression and anxiety being the most common illnesses, new research suggests.

The global study, which involved over 150,000 participants across 29 different countries, found that most mental health disorders first emerge in adolescence, highlighting the importance of investing in mental health services for young people.

Led by the University of Queensland and Harvard Medical School, and published in The Lancet Psychiatry, researchers analysed data from face-to-face interviews with adults collected between 2001 and 2022 as part of the WHO World Mental Health Survey initiative.

Lead author Professor John McGrath from the University of Queensland said the results demonstrate the high prevalence of mental health disorders globally, with 50 per cent of the population developing at least one disorder by the age of 75.

‘The most common were mood disorders such as major depression or anxiety,’ Professor McGrath said.

The researchers also found that mental health disorders varied between men and women. Men were more likely to suffer from alcohol abuse, and women more likely to develop post-traumatic stress disorder. Both sexes were commonly diagnosed with depression and specific debilitating phobias.

Mental health disorders were also found to typically first emerge in childhood, adolescence or young adulthood, with the peak age of first onset being 15 years of age. The median age of onset for men was 19, and for women it was 20.

Professor Ronald Kessler from Harvard Medical School stated that investment in mental health services should have a particular focus on young people.

‘Services need to be able to detect and treat common mental disorders promptly and be optimised to suit patients in these critical parts of their lives,’ he said. ’By understanding the age at which these disorders commonly arise, we can tailor public health interventions and allocate resources to ensure that appropriate and timely support is available to individuals at risk.’

According to the World Health Organization (WHO), a mental disorder is a ‘clinically significant disturbance in an individual’s cognition, emotional regulation, or behaviour’ resulting in heightened distress and impaired functioning.

In 2019, 97 billion people worldwide were suffering from a mental health condition, and by 2020 that number had risen significantly, with at least a 26 per cent increase in depression and anxiety caused by the Covid-19 pandemic.

A version of this article was originally published by our sister publication Nursing in Practice.

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